I drew a legal conclusion on "Good Morning America" Saturday that would have surprised the Dan Abrams who covered the George Zimmerman case leading up to, and shortly after, his arrest.

Now that the prosecution's case against Zimmerman is in, as a legal matter, I just don't see how a jury convicts him of second degree murder or even manslaughter in the shooting death of Trayvon Martin.

So what happened? How can an armed man who shot and killed an unarmed teen after being told by the police that he didn't need to keep following him, likely be found not guilty of those crimes?

I certainly sympathize with the anger and frustration of the Martin family and doubt that a jury will accept the entirety of George Zimmerman's account as credible. But based on the legal standard and evidence presented by prosecutors it is difficult to see how jurors find proof beyond a reasonable doubt that it wasn't self defense.

Prosecutors are at a distinct legal disadvantage.

They have the burden to prove that Zimmerman did not "reasonably believe" that the gunshot was "necessary to prevent imminent death or great bodily harm" to himself. That is no easy feat based on the evidence presented in their case. Almost every prosecution witness was called to discredit the only eyewitness who unquestionably saw everything that occurred that night, George Zimmerman.

He spotted Martin, became suspicious, called police, was told he didn't need to follow him, was only out of his car to give the authorities an address, was jumped and then pummeled by Martin and as he was being punched and having his head knocked into the ground, Martin went for Zimmerman's firearm and Zimmerman shot him once in the chest.

The prosecution, on the other hand, called 38 witnesses to try to show: Zimmerman was a wannabe cop who regularly reported black strangers in his neighborhood; initiated and was at least at one point, on top during the encounter; that Zimmerman's injuries were minor and that many aspects of his accounts to the police and media were inconsistent and/or lies.

For a moment, lets put aside the fact that many of the prosecution witnesses seemed to help Zimmerman in one way or another.

As a legal matter, even if jurors find parts of Zimmerman's story fishy, that is not enough to convict. Even if they believe that Zimmerman initiated the altercation, and that his injuries were relatively minor, that too would be insufficient evidence to convict. Prosecutors have to effectively disprove self defense beyond a reasonable doubt. So what exactly would that mean based on the facts as we know them?

Let's take a hypothetical, but realistic, scenario whereby jurors don't believe Zimmerman when he says he wasn't following Martin (the lead detective who seemed to find Zimmerman's account credible had a problem with this part of Zimmerman's account).

Let's also assume they believe Zimmerman approached Martin and it is only because Zimmerman was tailing Trayvon Martin that a fight ensued. First of all, the fact that there was a fight at all makes a murder conviction difficult. To win a murder conviction, they have to show he had the intent to kill and did so with "depraved mind, hatred, malice, evil intent or ill will."